A forwarding JSF ViewHandler implementation that produces URLs containing the
conversation id query string parameter. All methods except those which
produce a URL that need to be enhanced are forwarded to the ViewHandler
delegate.

A request parameter was chosen to propagate the conversation because it's
the most technology agnostic approach for passing data between requests and
allows for the ensuing request to use whatever means necessary (a servlet
filter, phase listener, etc) to capture the conversation id and restore the
long-running conversation.

Allow the delegate to produce the action URL. If the conversation is
long-running, append the conversation id request parameter to the query
string part of the URL, but only if the request parameter is not already
present.

This covers form actions Ajax calls, and redirect URLs (which we want) and
link hrefs (which we don't)